1. Field of the Invention
The present invention relates generally to an apparatus and method for retarding the splash of liquids discharged from a rotating workpiece and specifically to an apparatus and method for retarding the splash back of liquids collected from a rotating silicon wafer during the performance of processes upon the silicon wafer.
In the processing of semiconductor materials for the manufacture of integrated circuits and the like, a number of separate processes must be performed on the silicon wafers. Reference is made to U.S. Pat. No. 4,281,031 in which such different processing steps are set out. Typically, the various processing steps for silicon wafers involve the application of different liquids to the silicon wafer during which different types of waste liquids are generated. It is desirable during the processing of silicon wafers to have the waste liquids being generated continuously drained away from the silicon wafer and collected. This includes certain caustic waste fluids which must be drained from the silicon wafer. By rotating the silicon wafer waste, liquids will be discharged from the silicon wafer by centrifugal force. These waste liquids may be collected by a collection means which provides a solid surface against which the discharged waste liquids are captured and drained away. Upon contact with the collection means the force of the discharged waste liquids which is not absorbed by the collection means will cause a splashback effect whereby some of the waste liquids will splash away from the collection means and often be directed back towards the silicon wafer. In this way, waste liquids will not be efficiently collected and may interfere with the processing of the silicon wafer. It is therefore highly desirable to provide an apparatus whereby the waste liquids discharged from the rotating silicon wafer may be collected and drained away with a minimal amount of splash back.
2. Description of the Prior Art
The prior art discloses apparatus which use cup-shaped drains to collect liquids discharged radially from a rotating workpiece. However, no prior art reference discloses use of a rotating collection means to retard the splash of the fluids being collected. U.S. Pat. No. 4,281,031 provides a fixed cup-shaped drainage mechanism for collecting fluids discharged from a rotating workpiece. The drain is not rotated.
In other unrelated fields, this problem has also not been solved. U.S. Pat. No. 3,327,401 discloses a cup-shaped drain against which moisture discharged from rotating material is collected and drained. As for the prior reference, this cup-shaped drain is not rotated. U.S. Pat. No. 3,945,921 discloses a rotary centrifugal machine in which moisture is discharged by centrifugal force to the fixed wall of a cup-shaped drain. The present invention is distinguishable over these references by disclosing a collection means for liquids discharged from a rotating workpiece which collection means is rotated to retard splash.